Comparing Surgical and Non-surgical Treatments for Type 2 Diabetes in Adults Who Have Mild or Moderate Levels of Obesity

Research UpdateOct. 16, 2014

Two small clinical trials found that after one year of treatment, bariatric surgery may be more effective than non-surgical approaches for treating type 2 diabetes in adults who have mild or moderate levels of obesity. They also identified factors to be considered in planning further research. Previous studies demonstrated the benefits of bariatric surgical procedures for weight loss and for ameliorating type 2 diabetes, at least in the short term, in individuals with either extreme obesity (defined as a “body mass index,” or BMI, of 40 or more) or somewhat lower levels of obesity (BMI 35 to 40). However, there has been only limited research on this surgery in people with milder levels of obesity (BMI between 30 and 35). Thus, investigators recently conducted small clinical trials to gain preliminary insights into the risks and benefits of bariatric surgery, compared to non-surgical interventions, for type 2 diabetes in people with various levels of obesity. The trials also aimed to elucidate the challenges to be addressed in designing a more extensive study with larger numbers of participants.

In one of the clinical trials, investigators randomly assigned 69 volunteers to receive either bariatric surgery or an intensive lifestyle intervention for weight loss, and then compared health outcomes after a year. All of the participants had type 2 diabetes and mild to moderate levels of obesity (BMI between 30 and 40); most were women. Those assigned to surgery received either a Roux-en-Y gastric bypass (RYGB) procedure or laparoscopic adjustable gastric banding (LAGB). The intensive lifestyle intervention involved both diet and exercise and was delivered in an individualized format. After one year, about 50 percent of the individuals in the RYGB group and 27 percent of those in the LAGB group had partial diabetes remission. Their blood glucose (sugar) levels, although not quite normal, were no longer in the range of diabetes; and they were able to discontinue their diabetes medications. Several individuals in each surgical group achieved complete remission of their diabetes—normal blood glucose levels without need for diabetes medications. None of the people in the lifestyle intervention group had partial or complete diabetes remission. Participants in all of the groups lost weight; those in the RYGB group had the greatest weight loss. However, several individuals in the RYGB and LAGB groups experienced complications, including a surgery-related ulcer and dehydration.

In the other clinical trial, investigators randomly assigned volunteers with type 2 diabetes and obesity to receive either RYGB surgery or a lifestyle and medical intervention of diet and exercise, delivered in group sessions, with a weekly medication adjustment plan. Of the 38 participants analyzed in the study, a majority were women. After one year, 58 percent of the individuals in the RYGB group, but only 16 percent of those in the lifestyle and medical therapy group, saw their blood glucose levels improve to the target for glucose control chosen as the study outcome. Weight loss was greater in the RYGB group as well. Assessing the safety of the interventions, the researchers noted several serious adverse events among participants in the RYGB surgery group, including ischemic heart disease requiring coronary artery bypass surgery and depression with attempted suicide. In the non-surgical group, a few individuals experienced near-fainting.

The researchers also described important “lessons learned” from these clinical trials. A major challenge was recruitment. Each research team screened hundreds of potential volunteers, but only about 1 of every 10 individuals screened for one study and 1 of 20 screened for the other study were both eligible and interested in participating. In each study, several individuals stopped participating after being assigned to a group, but before receiving the intervention. Costs also posed a challenge because insurers do not currently cover bariatric surgery for people with lower levels of obesity. For these trials, the investigators obtained some funding for the surgical procedures either from their academic medical center or industry. The research aspects were supported by NIH. Finally, the types of bariatric surgery used in clinical practice continue to change over time; it may thus be valuable to study different surgical procedures in the future.

In summary, these small clinical trials add to preliminary evidence that bariatric surgery may be more effective than current non-surgical treatments for type 2 diabetes in individuals with mild to moderate levels of obesity. This research also highlights challenges to be met in designing larger and longer-term studies in the future, to gain more definitive data on risks and benefits.